Abstract: In order to promote effective use of limited underground space in tunneling operations, a Non-circular type of Shield Tunnel Boring Machine was developed. Utilizing existing technology for DK shield machine tunneling at the time, a modified type of tunneling was developed which has come to be commonly known as the DOT (Double O Tube) shield method. This DOT method was initially utilized in 1989 for the project of New Traffic System in Hiroshima Japan. Following the introduction of DOT type tunneling, another innovation, which featured an excavation of an arc square shape, has become known as DPLEX (Developing Parallel Link Excavating) shield method. The DPLEX method was initially developed and adopted for a sewage tunnel in Narashino Japan in 1994. The drastic idea of excavation utilizing the DPLEX method, made it possible to excavate various shapes, and brought a much smaller torque on the cutter and less abrasion of the bits.

Another innovation for excavating at great (vertical) depth, under high pressures was introduced, which has come to be known as the New DREAM method of excavation. The New DREAM method has been particularly developed for excavation in pneumatic caissons. The main benefit for the New DREAM method of excavation is the fact that soil in the working area is excavated and conveyed by remote-controlled machine. No man needs to work under high air pressures, thereby protecting working personnel and increasing the safety of the work place.